The tab to bribe at least one HISD trustee comes to as much as $150,000, according to evidence presented in federal district court Wednesday.

"It's just ... it's just the way they do business," construction company owner David 'Pete' Medford was heard saying on tape when discussing bribery at the Houston Independent School District.

This marked the third day of the civil trial and the first where Medford -- a key witness -- was on the stand. At the center of the trial is Larry Marshall, a former HISD trustee, and one of the most powerful.

The plaintiff, construction company Gil Ramirez Group, lost a contract with HISD and filed a lawsuit filed in 2010 alleging it was because they failed to pay a bribe to Marshall.

Marshall has admitted in depositions that his campaign treasurer Joyce Moss Clay had business relationships with companies seeking HISD contracts. Clay, in turn, admitted she had given a Marshall-owned consulting firm some of the proceeds from those companies. He denies any illegality as well as the bribery charges.

Medford, whose company is Fort Bend Mechanical, backed away from the $150,000 number under questioning Wednesday. The tape was made years ago.

"I may have said that," Medford said Wednesday from the stand. "I don't remember the exact amount."

When asked if the number of alleged bribes was over $100,000, Medford said, "Absolutely not."

HISD is not a defendant in the suit and won't comment except to say they will do their talking in court.

Other witnesses, including top HISD administrators, as well as former and current trustees, are expected to be called to the stand.

There is a chance that this trial will uncover a possible shady underbelly to the nation's fourth-largest school district.

For example, it's expected that jurors will hear about HISD's past connecting it to current issues involving the district's dismissed internal auditor, Richard Patton.

Patton was suspended in March, months after he questioned top district officials' rationale behind the HISD's massive $211 million bond shortfall and days after he spoke with the FBI, according to records and interviews. Patton was shown the door last month.

In court documents, Marshall has admitted he was under FBI investigation, but no criminal charges have been filed against Marshall, or anyone in connection with the case.

The trial is expected to last another two-and-a-half weeks and will begin Thursday at 10 a.m. at the United States Courthouse on Rusk.515 Rusk Avenue